As wafers transfer from station to station in a semiconductor manufacturing system, tolerance stack-up as well as handling problems, such as ESC sticking, result in wafer offset that causes process shift, which may ultimately lead to wafer loss. It is therefore desirable for the transfer robot to measure wafer offset and correct this offset at each station transfer.
Typically, multiple sensors are required to empirically and analytically derive the wafer center position. Sensors can be activated upon wafer movement, and a plurality of sensors can be used to determine the wafer's exact position in a station at a given moment. In one system, a robotic handling system is taught using an array of sensors positioned generally transverse to the path of movement of a substrate to detect the relative positions of the substrate for the purpose of precisely aligning the substrate relative to a predetermined destination point. In this system, a minimum of two sensors is required.
In another system, an apparatus, separate and apart from the processing system, utilizes a “spindle” type method where the wafer is incrementally rotated. This system does not take advantage of the direct movement of the wafer as it is transferred from the wafer storage cassette.
Another system requires an array of optical sensors positioned generally transverse to the linear path of the wafer support blade. Moreover, the wafer must pass over the sensors in a linear path transverse to the position of the sensors, which are positioned adjacent to the loadlock chamber. This makes this system ill suited to multiple chamber wafer processing systems.
In all these systems, multiple sensors are used to locate the wafer in-situ while the wafer is being transferred to or placed within a station. With multiple sensors in an array, each algorithm employed necessarily requires multiple sensor activation information, which is ultimately converted into multiple location coordinate points.
Thus, a need still remains for improved wafer handling systems. Further, wafer handling systems for loadlock chambers for loading and locking processing equipment, which require wafer cooling, are required. In view of the ever-increasing commercial competitive pressures, along with growing consumer expectations and the diminishing opportunities for meaningful product differentiation in the marketplace, it is critical that answers be found for these problems. Additionally, the need to save costs, improve efficiencies and performance, and meet competitive pressures, adds an even greater urgency to the critical necessity for finding answers to these problems.
Solutions to these problems have been long sought but prior developments have not taught or suggested any solutions and, thus, solutions to these problems have long eluded those skilled in the art.